A compact sound transducer, that is, an earphone, which converts an electric signal output from a reproducing device or a receiver into a sound signal by a speaker close to an ear or an eardrum, has been widespread. Since this type of sound reproducing device emits sound so that the sound can be heard only by a listener wearing the sound reproducing device, this type of sound reproducing device is being used in various environments.
Many of the earphones which are now in widespread use are shaped to be inserted into the ears of the listener. For example, an inner ear type earphone is a shape that is hung by an auricle of the listener. Furthermore, a canal type earphone has a shape used by being inserted deeply into the hole of the ear (ear canal), and since the canal type earphone is often structurally sealed type and the sound insulation performance is relatively good, there is merit such that music can be enjoyed even in a place where the noise is slightly large.
In general, the canal type earphone generally includes a speaker unit that converts an electric signal into a sound signal, and a speaker unit is attached to one end of the housing (outside of the ear canal) with a substantially cylindrical housing (housing) also serving as a sound tube as a basic component. The housing has a radiation outlet that radiates air vibrations generated by the speaker unit to the ear canal and transmits the air vibrations to the eardrum. In addition, an earpiece (detachable component) having a shape conforming to the ear canal is usually attached to the other end (insertion portion of the ear canal) of the housing when the listener wears the canal type earphone. For example, proposals have been made for a canal type earphone device that can accommodate a sound tube up to an ear canal entrance while storing the housing in a cavum conchae by disposing the sound tube obliquely from a position deviated from the center of the housing (see, for example, Patent Document 1).
Even while the listener wears the earphone and listens to a presented audio, it is necessary to listen to ambient sound at the same time, for example when people around the world speak. It is a dangerous situation that ambient sound cannot be heard, for example, when sports are conducted outdoors and indoors, including walking, jogging, cycling, mountain climbing, skiing, snowboarding, and during driving or navigation. Furthermore, the inability to listen to the ambient sound during communication or presentation causes a decline in service. However, most of the conventional earphones such as a canal type earphone are structured to close an ear hole almost completely in a wearing state, so that it is extremely difficult for the listener to hear ambient sound while listening.
Furthermore, the surrounding people view the listener as if the ear holes of the listener wearing the conventional earphone is blocked, which therefore gives the impression that it is difficult to talk to the wearer of the earphone, and also interferes with communication between people.